The invention relates to a cooling system that is intended for a thermoelectric power generator (TEG) that is arranged in an exhaust gas line of an internal combustion engine for generating electric power while utilizing the thermal energy of the exhaust gas.
The relevant prior art includes, for example, the German published patent application DE 10 2006 019 282 A1, which discloses an exhaust gas recirculation system that is provided for an internal combustion engine and includes an exhaust gas line and a fresh air line. In this case, the exhaust gas line and the fresh air line are connected in an exhaust gas conveying manner to an exhaust gas recirculation line. The exhaust gas recirculation line has an exhaust gas cooler, on which a thermoelectric power generator (TEG) is arranged with its hot side, in order to generate electric power. The proposed configuration provides an additional power generator with minimal effort and complexity. In order to have an adequate temperature gradient constantly on hand for generating electric power, the TEG is integrated on its cold side into the coolant circuit of the internal combustion engine.
European patent application EP 1 475 532 A2 also discloses an internal combustion engine having an intake line and an exhaust gas line. This internal combustion engine also has an exhaust gas recirculation system, with which the exhaust gas from the exhaust gas line can be fed back into the fresh air line through an exhaust gas recirculation line. This exhaust gas recirculation line also has a thermoelectric power generator (TEG), of which the hot side is arranged on the exhaust gas recirculation line, in order to generate electric power. In one special embodiment, the TEG has its own dedicated coolant circuit, which is intended for simultaneously cooling an electric inverter. The inverter, in turn, serves to control the speed of an electric engine, which can be operated alternatingly or simultaneously with the internal combustion engine, a so-called hybrid drive for motor vehicles.
Even if the cited prior art does not reveal any fundamental disadvantage, the object of the present invention is to utilize more efficiently the thermal energy of the exhaust gas.
This and other objects are achieved with a cooling system for a thermoelectric power generator that is arranged in an exhaust gas line of an internal combustion engine for generating electric power while utilizing the thermal energy of the exhaust gas. The TEG has its own coolant circuit, wherein the coolant circuit is provided for raising the temperature of the components of the internal combustion engine, the chassis, the transmission, and/or heating the passenger compartment.
Owing to the inventive configuration, the TEG represents in the final end an expanded exhaust gas heat exchanger. Therefore, in addition to its main function, that is, the generation of electric energy, there are also additional functionalities because of the uncoupling of the heat from the exhaust gas. These functionalities involve predominantly the cold start or rather the low load phases of the internal combustion engine. During these phases, the temperature of the transmission or rather the rear axle differential rises very slowly. The following functions for a faster temperature rise exist because of the TEG:
(a) promote the temperature rise of a passenger compartment of a vehicle by supplemental heating with the coolant circuit;
(b) fast temperature rise of the transmission lubricant with the coolant circuit;
(c) promote the temperature rise of the lubricant of the internal combustion engine and/or the components of the internal combustion engine and, thus, faster warm-up of the internal combustion engine; and
(d) fast temperature rise of the chassis components, such as the rear axle differential, by means of its lubricant.
In this respect, the distribution of the heat flows in the coolant circuit can ensue, for example, in a centralized system, by means of, for example, a multifunctional valve or in a decentralized system by means of a mono valve or a 2/2 way valve, as used, for example, in an integrated heating and air conditioning device. The result of the embodiment according to the invention is a significantly higher electric power output of the TEG and the possibility of operating the inventive design more flexibly than is the case with a TEG air cooling system. Reducing the load on the electric power generator reduces in an advantageous way the fuel consumption (reduction in CO2 emissions).
According to aspects of the invention, the major advantages lie in the added utility gained from a faster temperature rise of, for example, the transmission lubricants and the lubricants of the internal combustion engine, as well as from heating the passenger compartment. The inventive design also contributes in an advantageous way to a faster temperature rise of the TEG and slows down the cooling rate of the TEG at low load points.
In an especially preferred design variant for the cooling system of a TEG, a coolant pump and a heat exchanger are arranged in the coolant circuit.
In another embodiment, the coolant pump can be driven electrically or mechanically. This makes it possible to avoid “reheating” the TEG due to the after-flow of the coolant pump and, thus, a potential overheating of the TEG.
Preferred location sites for the heat exchanger include, for example, an internal combustion engine chamber, in a wheel assembly, and/or under the floor of a vehicle chassis.
In yet another embodiment, the internal combustion engine has a primary coolant circuit, wherein the coolant is operatively connected to the primary coolant circuit. In an advantageous way, this embodiment dispenses with the alternative throttling of the TEG coolant circuit by means of the coolant pump of the internal combustion engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.